This invention relates to stabilized aqueous hydrogen peroxide solutions containing an organic hydroxy compound and an organophosphorus compound in sufficient quantities to stabilize the hydrogen peroxide from decomposition in the presence of heavy metal ions, such as copper and iron, and in the presence of insoluble heavy metal sulfides, such as molybdenite and chalcopyrite. The stabilized aqueous hydrogen peroxide solutions of this invention are particularly useful in mining and mineral processing applications where high concentrations of heavy metal ions and heavy metal sulfides are present.
It is known that wasteful decomposition of hydrogen peroxide is catalyzed by small amounts of impurities, especially heavy metal ions. Aluminum cations are introduced into the hydrogen peroxide when aluminum containers and vessels, commonly used to store and handle hydrogen peroxide solutions, become corroded by such solutions. Calcium and magensium ions, and sometimes iron, copper and manganese ions are introduced into hydrogen peroxide solutions when such solutions are diluted with hard water, generally, at the site of use. In addition, it is well known that hydrogen peroxide is more stable in acidic solutions than in basic solutions.
The wasteful decomposition of hydrogen peroxide, which was referred to above and which is catalyzed by heavy metal ions, can be represented by the following equation: EQU 2 H.sub.2 O.sub.2 .fwdarw. 2H.sub.2 O + O.sub.2 ( 1)
many types of stabliizers have been proposed as inhibitors of this catalytic decompositon and have been added for that purpose to hydrogen peroxide solutions intended to be stored or shipped and later diluted for use.
Blazer et al., U.S. Pat. No. 3,122,417, disclose alkylidene diphosphonic acids as stabilizers for hydrogen peroxide solutions which are acidic or basic. In U.S. Pat. No. 3,387,939 to Reilly et al. there are disclosed stannate stabilizer compositions containing an alkylidene diphosphonic acid and acidic hydrogen peroxide solutions stabilized therewith. The presence of the alkylidene diphosphonic acid prevents the precipitation of the stannate by polyvalent cations, such as aluminum and calcium. Carnine et al., U.S. Pat. No. 3,383,174, disclose the use of a nitrilo trimethylene phosphonic compound in stannate stabilized peroxide solutions to preclude the precipitation of stannate by polyvalent cations.
Reilly, U.S. Pat. No. 3,687,627 discloses acidic stabilized hydrogen peroxide solutions containing a soluble stannate stabilizer, a soluble magnesium salt, an alkylidene diphosphonic acid or a soluble salt thereof and optionally a soluble pyrophosphate or fluosilicate. The magnesium compound serves as an effective stabilizer for the peroxide solution when it is rendered alkaline.
In U.S. Pat. No. 3,649,194 to Glanville there is disclosed the use of an organic hydroxy compound as stabilizer for acidified hydrogen peroxide solutions containing metal ions, particularly peroxide solutions useful for pickling copper. Useful organic hydroxy compounds disclosed therein are phenol, paramethoxyphenol, allyl alcohol, crotyl alcohol, and cis-1,4-but-2-ene-diol.
U.S. Pat. No. 3,701,825 to Radimer et al. is directed to the use of a water-soluble ethylenediamine tetra(methylenephosphonic acid) compound to stabilize aqueous hydrogen peroxide solutions over a pH range of at least 1.5 to 13.5 against decomposition by contaminants, such as cations or iron, copper and manganese.
With the exception of the Glanville patent, most of the prior art is directed to suppression of the wasteful decomposition of hydrogen peroxide under storage or shipping conditions or upon dilution at the user's site.
For some oxidation reactions, however, the H.sub.2 O.sub.2 may be employed under conditions of high concentrations of metal ions. Conditions are especially harsh where both dissolved metal and insoluble metal sulfides are encountered. For example, the dissolution of chalcopyrite with H.sub.2 O.sub.2 subjects the oxidizing agent to a number of decomposition catalysts: EQU CuFeS.sub.2 + 2H.sub.2 O.sub.2 + 4H.sup.+ .fwdarw. Cu.sup.++ + Fe.sup.++ + 2S.degree. + 4H.sub.2 O (2) EQU cuFeS.sub.2 + 8H.sub.2 O.sub.2 .fwdarw.Cu.sup.++ + Fe.sup.++ + 2SO.sub.4 = + 8H.sub.2 O (3)
in order to use effectively the H.sub.2 O.sub.2 for the desired reactions (2) and (3), the wasteful decomposition reaction (1) must be suppressed.
Thus, there is a need for hydrogen peroxide solutions which are stable over a wide pH range and under harsh conditions of use wherein relatively high concentrations of metal ions and insoluble metal sulfides are encountered.